Conventional automotive alternators are 3-phase alternators which have a stator and a rotor. The stator generally includes a stator core having three phases of conductors wound through the stator core. The stator core is typically constructed of a plurality of laminations stacked axially relative to the alternator's rotational axis. The rotor is generally a claw-pole or Lundell rotor and includes a number of alternating pole fingers which provides a circumferential surface facing the stator that alternates between north and south poles for generating an output current in the stator winding.
One drawback that is common to these alternators is a reduction in power output due to eddy current loss within the machine. In particular, the magnetic centers between adjacent pole fingers are spaced axially apart due to the inherent structure of the pole finger, which is generally a narrowing trapezoidal shape. As magnetic flux flows axially through the stator lamination stack from magnetic center to magnetic center, eddy current loss is induced. This eddy current loss dissipates electric power into waste heat and reduces the total output current from the alternator. It also increases the stator temperature and reduces the allowable ambient temperature of alternator operation. Due to these constraints, the conventional claw-pole alternator has an axial path distance between magnetic centers of adjacent pole fingers that is limited to about one-sixth of the height of the stator lamination stack (about 17% of the axial height).
Accordingly, there exists a need to provide an alternator having a claw-pole rotor which maximizes power output of the alternator while maintaining an acceptable level of eddy current loss.